Non-return, direction of rotation selecting device for synchronous motor

ABSTRACT

A non-return device for a synchronous motor comprising a rotor supported between two brackets and having no preferential rotation direction per se, an eccentric on the rotor axis, an arm mounted on said eccentric through one of its ends and at the other end a contact plug or crank pin and a groove (or port) in a bracket so as to receive said contact plug, this groove comprising thrust bearing means for said contact plug for one direction of rotation of the motor.

United States Patent 1191 Jullien-Davin 1 Jan. 9, 1973 s41 NON-RETURN,DIRECTION OF 3,501,657 3/1970 Heinzen et al ..310/41 ROTATION SELECTINGDEVICE FOR 3,501,658 3/1970 Morley ..310/41 .SYNCHRONOUS MOTOR FOREIGNPATENTS OR APPLICATIONS [75] Inventor Valence France 527,673 10/1940Great Britain ..310/41 [73] Assignee: Crouzet, Paris, France [22] Filed:July 26, 1971 Primary Examiner-D. F. Duggan Attorney-Holman & Stern [2]]Appl. No.: 166,204

[57] ABSTRACT U.S. A Hg-return device for a ynchronous motor com. [51]Int. Cl. ..H02k 7/10 prising a rotor supported between two brackets andField of Search 310/41, 162, 163, 68 having no preferential rotationdirection per se, an eccentric on the rotor axis, an arm mounted on saidecl References. Cited centric through one of its ends and at the otherend a UNITED STATES PATENTS contact plug or crank pin and a groove (orport) in a bracket so as to receive said contact plug, this groove3,333,125 7/1967 Grabow 3 10/41 comprising thrust bearing means for saidcontact plug 3,335,302 8/1967 Van der Linden ..3l0/4l for one directionof rotation of the motor.

3,403,273 9/1968 Higuchi ..3l0/41 3,501,656 3/1970 Morley ..310/41 4Claims, 8 Drawing Figures PATENTEDJAM 9 I913 SHEEI 1 BF 2 FIG FIG 2PATENTEDJAH ems 3110.155

SHEEIEUFZ NON-RETURN, DIRECTION OF ROTATION SELECTING DEVICE FORSYNCHRONOUS MOT R This invention relates to a silent non-return deviceapplicable to small single phase synchronous motors which, in theabsence of such a device, may rotate indifferently in one or the otherdirection. The device according to the invention further relates to asimple way of selecting the direction of rotation by actuating anexternal control member.

It is known that a large number of synchronous motors do not haveanypreferential direction of rotation and that it is a constant practice toprovide them, upon assembly, with a non-return device; however, ingeneral, in these motors, the direction of rotation is defined once andfor all and cannot be changed without.

dismantling the motor.

Silent non return devices are already known which consist of a ball (orroller) jamming system between a cylindrical member and another membercomprising a non concentric slope, one of the members being attached tothe frame, and the other being integral with the rotor. Such a device isapplied, for example, in French Pat. No. 1,149,195, but its drawback isthat the direction cannot be changed without dismantling the motor and,moreover, it is costly, for it requires great manufacturing precision,in particular, a perfect concentricity of the cylindrical member androtor.

Non-return devices are also known in which a catchlike element preventsrotation in one direction, as is the case, for example, in French Pat.Nos. 1,413,365 and NO. 1,391,124. These devices are less costly than thejamming devices, but while they may be simpler, they have thedisadvantage which resides in the fact that the choice of direction(through reversal of the catch) cannot be made without dismantling andespecially in the fact that the catch oscillates continuously from onethrust bearing to the other, which makes these devices quite noisy.

Finally, a direction selecting device has already been provided inwhich, as described in French Pat. No. 1,579,497, a member, mounted withsmooth friction on the rotor and provided with an elastic reset device,actuates a contactor-inverser so that, depending on whether the motor isenergized through one or the other terminal of the contactor-inverser,the motor rotates in one or the other direction; but this device turnsout to be rather costly because of the presence of electric contacts andleads to a rather substantial loss of torque due to the fact that themember mounted with smooth friction on the rotor must transmit, as apure loss, a sufficient torque to overcome the elastic reset and raise acontact.

A specific object of this invention is to provide a very economic, verysimple silent device which eliminates the drawbacks of previously knownsystems.

To this effect, the invention relates to a non-return device for asynchronous motor comprising a rotor supported between two brackets andhaving no preferential direction of rotation, per se, an eccentric onthe rotor axis, an arm mounted on said eccentric through one of its endsand, at the other end, a contact plug or crank pin and a groove (orport)-in a bracket so as to receive said contact plug, this groovecomprising thrust bearing means for said contact plug, for one directionof rotation of the motor. In one embodiment, the groove is shapedsubstantially as an L, one branch of which, directed essentiallyradially and in the direction of the motor axis, is sufficiently long toprovide clearance of the contact plug without the latter striking oneend or the other of its stroke, and the other branch of which isdirected cross-wise.

When the motor starts in the direction for which it has been built, thearm, through its natural friction on the eccentric tends to rotate inthe direction in which the contact plug of the arm abuts on the edge ofthe radial branch of the groove, opposite the cross-wise branch, and itslides freely against this edge.

On the other hand, when the motor starts in the incorrect direction, thecontact plug slides on the edge of the radial groove which isinterrupted by the cross-wise branch and, as it penetrates in thecross-wise branch, it blocks the rotor which, then, can start again onlyin the correct direction.

The silent non-return device according to the invention can also be usedto provide a particularly simple rotation direction selector; thecontact plug enters into a wide rectangular groove arranged radially onthe fixed bracket of the motor. The length of the groove is sufficientto provide clearance of the contact plug so that it does not strike theone or the other end of its strokeandthe width is slightly greater thantwice the diameter of the contact plug. A member which may occupy twopositions creates an obstacle to the clearance of the contact plug alongone or the other of the radial edges of the groove; it is clear that themotor can rotate only in the direction for which natural friction of thearm on the eccentric maintains the contact plug, against the radial edgeof the groove, free of any obstacle. g

The movable member, which may occupy two positions, can be a pivotingtipping device controlled manually or through a cam, a movable magneticarmature controlled by an electromagnet or a thermal switch heated by anelectric resistor.

When using an electromagnet control, advantageous economic solutionconsists in energizing said electromagnet in series with the motor andin providing a contact which, when it is closed, shunts the terminals ofthe coil which is then not in use and which, when it is opened, leavesthe coil in use; this arrangement makes it possible to provide the coilwith very few turns and a low impedance, i.e., with the minimum weightof copper.

The invention will be more fully understood as a result of the followingdetailed description with reference to the appended drawing which isgiven as a nonlimiting example in which:

FIG. 1 is a partial sectional view of a motor along the rotor axis;

FIG. 2 is a partially broken away top view of the motor shownin FIG. 1;

FIG. 3 is similar to FIG. 2, but for the opposite direction of rotationof the motor;

FIG. 4 is similar to FIG. 2, but for a varying embodiment;

FIG. 5 is identical with FIG. 4, but for another position of themechanism;

FIGS. 6 and 7 are identical with FIG. 3 but for other varyingembodiments;

FIG. 8 is a wiring diagram relating to the varying embodiment of FIG. 7.

FIG. 1 is a sectional view of a synchronous motor comprising, in a knownmanner, two brackets l and 2 made of magnetic material, from which poles1a and 2a are obtained, which are arranged on a cylindrical surface. Acoil 3 is located outside this cylindrical surface and a rotor made offerrite 4, attached to an axis 5 through a plastic filler core 6 ismounted inside this cylindrical surface. A slight spring 7 and anintermediate washer 8 eliminates the axial backlash of the noisegenerating rotor. Axis 5 is guided in bores in brackets l and 2.According to the invention, the synchronous motor comprises an eccentric6a integrally molded with core 6, an arm 9 mounted freely on thiseccentric and a cylindrical contact plug 10 or crank pin mounted at theend of arm 9 and entering into a groove 11 (or port) arranged radiallyin bracket 1. As the motor rotates, natural friction between arm 9 andeccentric 6a causes the arm to have a tendency to rotate and causescontact plug 10 to be amaintained in contact with one of the edges ofthe groove or port 11. The fact that arm 9 is slightly thicker thaneccentric 6a and that washer 8 bears elastically on arm 9, enhancesnatural friction between rotor 6 and the arm, but the device can operatewithout this increase in friction.

FIGS. 2 and 3 are top views of the motor shown in FIG. 1, in which, forpurposes of clarity, only eccentric 6a, axis 5, arm 9 with its contactplug 10 and a part of bracket 1, comprising groove (or port) 11 havebeen left, thus providing a good understanding of the operation. It canbe seen that the radially directed groove or port 11 comprises across-wise branch 11'. In FIG. 2, it has been assumed that the motorstarted in the counterclockwise direction, arm 9 having a tendency torotate with rotor 6 and eccentric 6a; contact plug 10 came into branch11' of the groove in which it has no room for clearance and as it bearson projection 11a, the motor is blocked and can start again only in theother direction. On the other hand, FIG. 3 shows what happens when themotor starts in the clockwise direction contact plug 10 comes againstedge 11b of groove (or port) 11 and oscillates freely between its twoextreme positions l0l0", shown as a dotted line.

FIGS. 4 and 5 show how the device can be fitted up as a selector of thedirection of rotation (components already denoted in FIGS. 1-2-3 havethe same reference numbers). The groove or port 11 is, in this case,rectangular and radially directed and its width is substantially equalto twice the diameter of contact plug 10. A movable member or tippingdevice 13 pivoting on an axis 14 integral with bracket 1 is providedwith a bent end 13a entering into port 11. If the bent part 13a occupiesthe upper corner of groove or port 11 (FIG. 4), the motor can turn onlyin the clockwise direction.

On the other hand, if part 13a occupies the lower corner of groove 11(FIG. 5), the motor can rotate only in the counter-clockwise direction.

FIG. 6 shows an embodiment in which the movable member is a thermalswitch 13' attached to a support 14', itself integral with bracket 1.Depending on whether a heating electric resistor 15 is energized or not,part l3'a of the thermal switch entering into port 1 1 is in theposition shown as a solid line or in the positron shown as a dotted lineand the motor rotates in the one or the other direction.

FIG. 7 shows how the movable member 13 can be elastically controlled inone direction by a spring 16, and in the other, by an electromagnet 17when coil 18 is energized.

Finally, FIG. 8 shows how the coil of electromagnet 18 can be connectedin series with winding 19 of the motor and how its terminals can beshort-circuited by closing a contact 20 so as to switch off said coil18. This solution makes it possible to use a very cheap coil 18 with avery low impedance, using very little copper wire.

What I claim is:

l. A non-return device for a synchronous motor comprising a rotorsupported between two brackets and having no preferential rotationaldirection per se, an eccentric on the rotor axis, an arm mounted on saideccentric through one of its ends, a contact plug or crank pin disposedat the other end thereof, a groove or port disposed in a bracket so asto receive said contact plug, said groove comprising thrust bearingmeans for said contact plug for one direction of rotation of the motor,said groove or port being rectangularly shaped and being radiallyoriented in the bracket, said device further including a movable membermeans which may take up two positions so as to occupy one or the othercorner of said rectangular groove, said corners being opposite saideccentric with respect to the groove, said movable member means markingoff, in the groove, for the arm contact plug, a free space shaped as anL whose cross-wise branch is oriented at will so as to compose onerotational direction over another.

2. A non-return device according to claim 1, wherein the two-positionmovable member means is a thermal switch heated by an electric resistor.

3. A non-return device according to claim 1, wherein the two-positionmovable member means is the movable armature of an elastic resetelectromagnet.

4. A non-return device according to claim 3, comprising a low impedanceelectromagnet coil having very little copper wire, energized in serieswith the electric motor winding and a contact providing for theshortcircuiting of the coil terminals.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION ratent 3.710.155Dated January 9, 1973 Inv Jean Jullien Davin It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

[30] Foreign Application Priority Data July 31, 1970 French No. '7028546 Signed and Sealedthis Nineteenth D3) Of October 1976 [SEAL]AIIESI.

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner nflarenlsand Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent 3. 710. 155 Dated January 9, 1973 Inven Jean Jullien-Davin It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

[30] Foreign Application Priority Data July 31, 1970 French No. 70 28546Signed and Scaled this Nineteenth D a y 0 f October 1976 SE AL] A ttest:

RUTH C. MASON C. MARSHALL DANN Altesring Officer (ummixsiuner of Parentsand Trademarks

1. A non-return device for a synchronous motor comprising a rotorsupported between two brackets and having no preferential rotationaldirection per se, an eccentric on the rotor axis, an arm mounted on saideccentric through one of its ends, a contact plug or crank pin disposedat the other end thereof, a groove or port disposed in a bracket so asto receive said contact plug, said grOove comprising thrust bearingmeans for said contact plug for one direction of rotation of the motor,said groove or port being rectangularly shaped and being radiallyoriented in the bracket, said device further including a movable membermeans which may take up two positions so as to occupy one or the othercorner of said rectangular groove, said corners being opposite saideccentric with respect to the groove, said movable member means markingoff, in the groove, for the arm contact plug, a free space shaped as anL whose cross-wise branch is oriented at will so as to compose onerotational direction over another.
 2. A non-return device according toclaim 1, wherein the two-position movable member means is a thermalswitch heated by an electric resistor.
 3. A non-return device accordingto claim 1, wherein the two-position movable member means is the movablearmature of an elastic reset electromagnet.
 4. A non-return deviceaccording to claim 3, comprising a low impedance electromagnet coilhaving very little copper wire, energized in series with the electricmotor winding and a contact providing for the short-circuiting of thecoil terminals.